Conventionally, in an observation trip regarding an installation for a factory, or the like, observers observe an actual installation or facility, or observe a prepared panel or video. On the other hand, for example, Patent Document 1 proposes a system to overlay-display element information corresponding to the site on an actual site image imaged by a portable terminal or the like, according to the movement of an observer.
In dangerous worksite areas, e.g., at a factory or a construction site, the dangerous area is indicated, with a visual warning such as paint, a sign or other posted warning. Since indications of these dangerous spots (dangerous spot indications) are stationery, in general, indications and signs are posted throughout the range where there may be a danger.
There may be cases where a dangerous area is always dangerous, and there may be cases where it is dangerous only during a particular period of time. For example, crane operation site in a factory, the area below a hanging load becomes a dangerous spot only when the crane is in operation.